BYTETOOLS

PDF Image Resolution Checker

Find every image placed in a PDF and see its effective DPI at the size it is actually printed, with low-resolution pictures flagged against your limits.

Drop a PDF here or click to browseImage placements are measured in your browser — nothing is uploaded

Effective DPI is the image’s pixel count divided by the size it is actually printed at: a 1,200 px picture placed 4 inches wide prints at 300 DPI, and the same picture stretched to 8 inches drops to 150.

What is the PDF Image Resolution Checker?

A 300 DPI photograph is only 300 DPI at its original size. Stretch it to twice the width on the page and it prints at 150 — which is why print jobs come back looking soft even though the source images “were high resolution”.

  • Effective DPI for every image placement, not just the stored pixel size
  • Tracks the full transformation matrix, including inside nested forms
  • Separate thresholds for colour images and 1-bit line art
  • Low-resolution placements highlighted in red
  • Reports the printed size of each image in inches
  • CSV export and fully local processing

How to use the PDF Image Resolution Checker

  1. 1

    Drop the PDF onto the upload area — every page is scanned automatically.

  2. 2

    Set the minimum DPI you accept for colour images and for line art.

  3. 3

    Tick “Show only images below the threshold” to see just the problems.

  4. 4

    Read the table: page, pixel size, printed size in inches and effective DPI.

  5. 5

    Export the whole table as CSV for your preflight notes.

About the PDF Image Resolution Checker

A 300 DPI photograph is only 300 DPI at its original size. Stretch it to twice the width on the page and it prints at 150 — which is why print jobs come back looking soft even though the source images “were high resolution”. Effective DPI is the number that matters, and it is the number this tool reports.

It walks each page's drawing operators, tracks the transformation matrix through every save, restore, transform and nested form, and at each placed image divides its pixel width by the width it actually occupies on the page. Line-art masks are measured separately, because they need far more resolution than a photograph.

Set your own thresholds — 300 DPI for colour and greyscale, 1200 DPI for line art are the usual print-shop defaults — and anything below them is highlighted. Everything runs in your browser and the full table exports as CSV for a preflight report.

Frequently asked questions

What is effective DPI in a PDF?

Effective DPI is the image's pixel count divided by the size it is actually printed at. A 1,200 pixel wide picture placed four inches wide prints at 300 DPI; stretch it to eight inches and it drops to 150. Scaling an image up on the page lowers its effective resolution.

What resolution do I need for printing?

300 DPI effective is the usual minimum for colour and greyscale photographs, and 1,200 DPI for 1-bit line art and scanned signatures. Large-format work viewed from a distance can go much lower — ask the printer before assuming.

The same image appears several times in the list. Why?

Each row is a placement, not an image. If one logo is drawn on twenty pages at different sizes, each placement gets its own effective DPI — which is exactly what you need to know.

My PDF shows no images at all. Is something wrong?

Probably not. A PDF built from text and vector artwork has no raster images to check, and vectors stay sharp at any size. The check only applies to placed bitmaps.

Is the file uploaded to be analysed?

No. pdf.js reads the page operators inside your browser tab. The document never leaves your device and nothing is stored.

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